Gravity davit



April 22, 1941. sc A 2,239,253

GRAVVITY mwn Filed March 29, 1940 mun-3 r KI:

- .Zzrevj ,5? pjaz yf Patented Apr. 22, 1941 GRAVITY DAVIT Ane P. Schat, Utrecht, Netherlands Application March .29, 1940, Serial No. 326,763 In Germany March 20, 1939 3 Claims.

This invention relates to gravity davits for launching boats from ships, and more especially to the means for suspending from the davit heads the sheaves on the boats, which, together with sheaves at the davit heads, serve for guiding the falls by means of which the boats are lowered and hoisted.

In known constructions, an eye of the sheave block on the boat is normally engaged by a hook integral with the davit head. This hook should be shaped and sized as to allow said block to slip off only when the davit, in moving on its trackway downhill towards the water under the gravitational pull of the boat, has reached, or nearly reached its extreme outward position. On the other hand, said hook shall not prevent disengagement of said block on the high side of a ship having a certain amountof list.

In view of the incompatibility of these conditions, the hook is ordinarily sized as to disengage the block on the boat in the extreme outboard position of the davit on the high side of a ship having a list of This still allows the boat to be launched when the ship is on a level, but on the low side of a ship having any appreciable list the block on the boat is then likely to disengage the hook prematurely and thus prevent the davit from moving outward or lufiing through a suflicient distance.

It has already been suggested to pivot the suspension hook to the davit head and to connect it directly to one end of a draw member, for instance a cable, whose other end is secured to a relatively fixed part of the ship in such a manner that the hook is caused to swing about its pivot and thereby to release the sheave block on the boat when the davit has nearly reached the outboard end of its trackway. This prior construction, however, has similar disadvantages as the one referred to hereinbefore, since the moment wherein the flexible member is drawn taut so as to release the sheave block is not exclusively dependent on the rate of outward davit movement, but also on the magnitude of the list of the ship, if any.

My present invention has for its object an improved suspension means of the type just referred to, wherein the sheave block on the boat is released from its suspension hook the moment wherein the gravity davit, owing to paying out of the boat falls, has reached, or nearly reached its extreme outboard position, irrespective of whether the boat is on the high or on the low side of the listed ship.

With this and other objects in view, my invention comprises a suspension hook pivotally mounted for swinging movement in a casing pivoted to the davit head, said hook being provided with an upwardly extending arm having a face, which normally is concentric with the pivot of the casing and slidably engaged by the draw member.

In order that my invention may be more fully understood, reference is had to the annexed drawing, which shows a representative embodiment. After considering this example, skilled persons will understand that many variations may be made without departing from the principle disclosed, and I contemplate the employment of any structures that are properly within the scope of the appended claims.

Fig. 1 is an elevation in a transverse plane of a ship with gravity davit mechanism embodying the invention in one preferred embodiment installed thereon, the showing being somewhat diagrammatic with non-essential parts omitted for illustrative clearness, the full lines showing the davit in its normal or stowed position, and the dotted lines showing it in its extreme outboard position ready for launching a boat (not shown) suspended from its hook.

Fig. 2 is a side elevation from outboard of Fig. 1, showing only, on an enlarged scale, the davit head with associate parts.

Fig. 3 is a section taken on line IIIIII in Fig. 2.

A casing 5 is connected to the head of the ships davit 4 through a pivot 6 so as to be adapted for swinging movement athwartships relative to the davit. Said casing has a bottom recess 1 adapted to receive an eye 8 of the sheave block 9 on the boat. Mounted in casing 5 is a second pivot l0, which is arranged in parallel relation with pivot 6 and supports a doublearmed lever II. The lower arm ll of this lever forms the suspension hook for engaging the eye 8 of the sheave block 9, the upper arm ll having its outboard face normally concentric with pivot 5.

Pivoted to the davit head are two suitably spaced sheaves l9 and 20, and the boat fall 2| is passed over sheaves 9, l9 and 20 in a manner well known in the art. By paying out said fall, the davit, with or without a boat suspended therefrom, is allowed to move outwards by gravity, whereas the return movement is brought about by hauling in the fall.

The draw member referred to above comprises an eye I2, which embraces with some clearance the lever arm I l and is secured to the outer end of a draw bar I3 loaded by a spring I-I tending to force the bar outwards. Said bar and spring are accommodated inside the profile of the davit 4. The inner end of bar I3 is engaged by one arm of a bell crank I5, the other arm of which is connected, through a cable I6, to a hook I! secured to the trackway of davit I. The operative length of cable I6 can be adjusted, by means of a coupling nut I8, in such a manner that, in the outward movement of davit 4, with or without the boat suspended therefrom, and just before the arrival of the davit in its extreme outboard position, bell crank I5, under the pull of the then taut cable I6, swings to an extent as to cause, through the medium of draw bar I3 and against the action of spring I4, the lever I I to be rotated in clockwise direction through an angle allowin the hook I I to disengage the eye 8.

Since the casing 5 and the double-armed lever II, by the action of the gravitational force and owing to their hinged connection to the davit through pivot 6, tend to assume an invariable position relative to the vertical, irrespective of the magnitude of any list the ship may have, and since, moreover, swinging movement of casing 5 with lever II about pivot B does not affect the draw bar l3, owing to the fact that the eye I2 of said bar is adapted to move on the concentric outer face of the upper arm II. of said lever, it will be clear that the operation of the boat releasing means described is not in any way affected by said list.

If the boat, after lowering, is again hoisted by hauling in of the fall 2| until the eye 8 of sheave block 9 has entered the bottom recess of casing 5, further hauling in of the fall will cause the davit to return from its extreme outboard position to its inboard position. During this return movement, draw bar I3 has to be forced outward by spring I4, so that the eye I2, by its engagement of the inner face of arm II may impart counter-clockwise swinging motion to lever II to restore the engagement between suspension hook II and eye 8. With a view thereto, it is necessary for spring I4 to be strong enough to overcome any gravitational pull and frictional resistances of bell crank I5 and cable I6.

What I claim is:

1. In combination with a ships davit of the gravity type, a casing pivoted to the davit head so as to be adapted for swinging movement athwartships relative to the davit, a doublearmed lever mounted on said casing for swin ing movement athwartships relative thereto and comprising a lower arm forming a suspension hook for a life boat and an upper arm having a face normally concentric with the pivot of the casing, and a draw member having its one end adapted to slidably engage said face and its other end secured to a relatively fixed point of the ship.

2. In combination with a ships davit of the gravity type a casing pivoted to the davit head so as to be adapted for swinging movement athwartships relative to the davit, a doublearmed lever mounted on said casing for swinging movement athwartships relative thereto and comprising a lower arm forming a suspension hook for a life boat and an upper arm having a face normally concentric with the pivot of the casing, a draw bar mounted in the davit head for lengthwise sliding movement and having its one end formed as an eye loosely engaging the said upper lever arm in the region of said concentric face, a spring loading said draw bar so as to tend through said bar to hold said suspension hook in a position substantially vertically below the casing pivot, and a flexible element associating the opposite end of the draw bar with a relatively fixed point of the ship.

3. In combination with a ships davit of the gravity type, a casing pivoted to the davit head so as to be adapted for swinging movement athwartships relative to the davit, a doublearmed lever mounted on said casing for swinging movement athwartships relative thereto and comprising a, lower arm forming a suspension hook for a life boat and an upper arm having a face normally concentric with the pivot of the casing, a draw bar mounted in the davit head for lengthwise sliding movement and having its one end. formed as an eye loosely engaging the said upper lever arm in the region of said concentric face, a spring loading said draw bar so as to tend through said bar to hold said suspension hook in a position substantially vertically below the casing pivot, a bell crank pivoted to the davit and having its one arm engaged by the opposite end of the draw bar, and a flexible element connected with its one end to the second bell crank arm and with its other end to a relatively fixed point of the ship.

ANE P. SCHAT. 

